compatibility of RFC 4666 to RFC 3332

Hi Folks, 

There seems to be some confusion about this.  My understanding
after checking with the editors is that RFC 4666, although it
obsoletes RFC 3332, is still backwards compatible.  An implementation
of 4666 should be able to work with an implementation of 3332
and vice versa, thus there was no reason for a version change.  

The SSN and CIC were removed from Routing Key registration due
to interoperability issues, but these were optional parameters
in RFC 3332.

Cheers,

L. Ong